Amplifier assembly

ABSTRACT

The invention concerns a pressure amplifier that includes a low pressure inlet for supplying a medium at low pressure, a low pressure piston with a first operational area and at least one high pressure piston with a second operational area, the second area being smaller than the first area, and at least one high pressure outlet.

This application claims the benefit of Danish Application No. PA 200201820 filed Nov. 25, 2002 and PCT/DK2003/000802 filed Nov. 24, 2005,which are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

The present invention concerns a pressure amplifier, including a lowpressure inlet for supplying medium at low pressure, a low pressurepiston with a first operational area and at least one high pressurepiston with a second operational area, the second area being smallerthan the first area, and at least one high pressure outlet.

This type of pressure amplifier is particularly used in hydrauliccircuits, where the hydraulic pump integrated in the system cannot yieldsufficiently high pressure for all applications. For a part of thehydraulic circuit it is not desirable either to operate with a hydraulicmedium under such high pressure, since this make demands on the designof the hydraulic lines, joints between lines and the elements such asjoints, valves, check valves etc., which do not necessarily need to bedimensioned for high pressure. Thus, a cost factor is also involved formaking so low pressure in so large part of the hydraulic circuit aspossible, and by inserting pressure amplifiers providing a high pressurewhere necessary.

In connection with the present invention, the terms low pressure andhigh pressure are used. As the principles underlying the invention areequally applicable at different pressures, low and high pressure,respectively, are only to be understood so that the two media havedifferent (or same) pressure.

Furthermore, within the technical field it is commonly known how checkvalves are functioning, as well as the provision of return ducts, mediumreservoirs, and the like, to the required extent are regarded as amatter of course for the skilled in the art. To the extent they areintegrated in the apparatus and the system, respectively, and are notused directly in connection with the basically new and inventiveprinciple of the invention, these are omitted to wide extent for thesake of clarity.

The medium that drives or is set under pressure and which is used inconnection with the present invention is often hydraulic oil, but may beany other kind of liquid, including particularly water or a gas which isfound suitable for use in this type of systems. Furthermore, the systemand the pressure amplifier may be used by gases, including particularlyair, as the pressure amplifier and the system in its structure areconfigured so that the possible compressibility of the gases does nothave any influence on the function of the pressure amplifier.

Pressure amplifiers of the kind mentioned above are particularly used inhydraulic circuits, including particularly in cranes, trenchers,excavators, forklift trucks or corresponding machines, where great forceis to be applied for lifting or moving material. For the operator ofthese machines, it is very desirable to dose the force to the work toolsas accurately as possible. Another important aspect is to utilise theapplied energy the most possible, i.e. to design a pressure amplifierand a pressure amplifier system with a minimal loss of pressure.

In a known pressure amplifier, as e.g. described in WO 8607118, is knowna double acting pressure amplifier in which a central double-actingpiston device provided within the pressure amplifier cylinder displacesa pre-selector that acts as a kind of servomechanism for a changeovervalve, whereby liquid is continually allowed at low pressure by pushingon the low pressure pistons, so that the latter actuate a high pressurepiston which via a rod transmits the high pressure to a possibleactuator. The pre-selector is following the movement of the low pressurepistons slidingly, after which the valve opening is continually changed,so that at the middle of the stroke of the piston there will be fullyopen for the valve, whereby the opening, concurrently with the lowpressure piston reaching the end of its stroke, will close more and moreand thereby throttle down the intake of low pressure medium. Besides,there is provided a large number of springs, unions, and liquid ducts inand around the cylinder jacket, which otherwise co-operate with a numberof sealing rings and screwed in shafts for providing low pressure liquidon the correct side of the low pressure pistons, so that these will beactuated for pressing the high pressure piston forwards for providinghigher pressure.

In general, for this type of pressure amplifiers it applies that it isthe effective operational area of the low pressure piston relative tothe effective area of the high pressure piston that indicate the actualpressure amplification factor. For incompressible media, in theory thepressure amplification factor is directly proportional with the ratiobetween the two above mentioned areas. Actually, by a pressure amplifieras specified in WO 8607118 there will occur a relatively great energyloss in connection with supply of low pressure oil, as the oil is usedfor controlling the changeover valve, whereby losses arise in supply andrelief ducts, as well as the shifting of the valve causes a pressingback and/or consumption of oil, whereby in practice a very substantialenergy loss arises.

It is thus the purpose of the invention to provide a liquid or gasdriven pressure amplifier that utilises all of the incoming energy forwork energy.

Besides, it is a purpose to provide a pressure amplifier that does nothave space demanding differential areas, whereby the entire operationalarea on the side operating at any time is utilised 100%, so that theenergy from the drive medium is deposited as kinetic energy when movingthe main piston. The other side of the main piston is simultaneouslyconnected to a tank so that no overpressure is to be overcome.

Furthermore, the invention has the purpose of providing a changeovervalve which becomes activated by the movement of the main piston in sucha way that a possible flow loss and thereby pressure loss is therebyminimised. In the same connection, it is important to control thechangeover valve under all conditions so that the pressure amplifier, atlow as well as high operational frequencies and by rapid pressurechanges will function with great certainty. This is particularlyinteresting where the pressure amplifier is to operate at a high rate,i.e. many directional changes per minute.

It is thus a further purpose of the invention to provide a pressureamplifier that via its construction becomes cheaper and more compactthan the hitherto known amplifiers, simultaneously with being providedgreater power and greater reliability.

SUMMARY OF THE INVENTION

The invention provides for these problems by means of pressure amplifierwhich is peculiar in that a low pressure area communicates with aoperational chamber, which is limited by a low pressure piston and asurrounding cylinder; where at least one high pressure piston isprovided interacting with the low pressure piston, and that the highpressure piston is co-axially arranged in a high pressure cylinderrelative to the low pressure piston; that a changeover valve iscoaxially arranged in the cylinder, and that in connection with thevalve and for interaction with it there is arranged at least one springcoaxially around an impulse rod; that the spring is arranged to becompressed so that a spring loaded locking mechanism is instantlyreleased, the locking mechanism being built up of one or more springsthat press a locking member against a corresponding lock abutment formedin the valve, so that the valve shifts and opens for medium supply tothe operational chamber, whereby the low pressure piston, via contactwith the high pressure piston, is moving the latter towards the highpressure outlet due to supply of medium to the operational chamber,whereby this tightens a spring which in the end position releases thelocking mechanism whereby the valve shifts and the low pressure medium,via the low pressure connection via check valve, presses the high andlow pressure pistons in opposite direction, whereby the displaced mediumis conducted back to the tank.

By this construction, where the changeover valve is in one of twopositions during largely the whole process with pressing the lowpressure oil and thereby the low pressure piston forward and back,respectively, succeeded by a instantaneous change-over due to thelocking mechanism, it is achieved that the pressure medium intake is notthrottled down. When the flow ducts, i.e. the ducts of the pressuremedium, are held fully open during the entire movement of the pistons,however except the milliseconds when the spring-loaded changeover valvejumps from one position to another, it is achieved that the pressureloss in the pressure amplifier becomes negligible. Furthermore, it isachieved that by high cyclic change-over speeds, i.e. high operationalfrequencies, the operation becomes more accurate, as the function of thechangeover valve can be compared with an on-off situation so that it isnot an area where less pressure medium is supplied gradually, but thereis full pressure medium or no pressure medium.

At the same time, the construction is substantially simplified comparedwith prior art, as all moving parts are concentrically arranged about acentre line. This implies a considerable reduction in the machining stepof cylinders and pistons, as well as the number of parts can be reducedsubstantially.

The different pistons, valves, springs and rods are held in position bymeans of locking rings, as e.g. Seeger rings, O-rings, bayonet coupling,or similar.

By furthermore choosing the springs so that compression, meaning theenergy accumulated in the spring, corresponds to the releasing pressureof the locking mechanism and thereby the springs forming part of thespring constants of the locking mechanism in such a way that the forcein the locking mechanism is surmounted at the maximum compression of thespring arranged coaxially around the impulse axis, the instantaneous,very sudden change-over from movement in one direction of the lowpressure piston to movement in the opposite direction of the lowpressure piston is achieved.

In a further, preferred embodiment of the invention, the lockingarrangement has been built up in at at least one boring providedradially in the low pressure cylinder, and that in the boring a lockingelement has been provided, e.g. in the shape of a ball, the ballinteracting with a spring so that the ball is pressed down into one oftwo recesses with dimensions corresponding to the part of the ballprovided in the cylindric surface of the valve. Instead of a ball, otherelements may be used, e.g. a cylindric pin with a rounded top, or awedge-shaped element with corresponding profile provided in the surfaceof the valve.

It is a preferred embodiment of the locking mechanism, which is simplyestablished by two indentations being arranged at the outer side of thevalve body, so that the locking element, e.g. the ball or one of thecorresponding elements described above, are pressed down into the firstrecess by means of the spring force from the spring of the lockingmechanism. The recesses have partially circular cross-sections, wherethe diameter corresponds to the ball diameter or is designed with across-section corresponding to the shape of the locking element. Whensubsequently the low pressure piston moves forward under influence ofthe medium pressure, the spring around the impulse axis will becompressed until a spring force is achieved, the spring force beingnecessary to overcome the lodging of the ball in the valve body, afterwhich this is pressed up against the springs in the locking mechanism,and the valve suddenly changes its setting. This instantaneous,mechanical change-over from one situation without using drive medium forthe second situation implies that there is substantially less flow lossin the pressure amplifier. By the known pressure amplifiers, a flow lossof 30-50% is expected, where by experiments with pressure amplifiersaccording to the present invention it has appeared that the flow lossbecomes substantially less, namely about 8%.

In a further, preferred embodiment of the pressure amplifier, thelocking arrangement is built up in an annular, flat groove provided atthe inner side of the low pressure cylinder, so that at least twoU-shaped locking blocks are arranged in the groove, the locking blocksbeing chamfered at the ends, that a number of radially oriented boringshave been provided, corresponding to the number of locking members, andthat in each boring there is arranged a spring pressing the blockstowards the centre line of the cylinder so that the chamfered ends ofthe blocks co-operate to hold a locking element arranged in the valve inone of two positions on respective chamfered sides of the blocks,whereby a functionally reliable locking arrangement is also achieved.

By taking advantage of the principles of production used for the innermachining of the surfaces of the cylinders, there may advantageously bearranged an extra groove in connection with the locking mechanism. Theblocks will then have shape as two U-shaped locking blocks where at thefree ends chamfered edges have been provided. The chamfered edges areused for abutment against a locking element, e.g. in the form of arod/pin provided in the body of the changeover valve. In the same way asdescribed above in connection with the ball lock, due to thedisplacement of the low pressure piston a spring stress will be built upin the spring arranged coaxially about the impulse rod, this forcepressing the rod against the chamfered sides in the locking blocks. Whenthe force attains a certain size, the rod will be pressed through thechamfering by overcoming the spring force in springs arranged in thelocking mechanism. At the moment the spring force in the impulse rodreaches that level, the change-over in the valve will occurinstantaneously, and the changeover valve will be held in the newsetting until the position again reaches a size by which the pin/rod maypress the two chamfered sides on respective locking blocks away fromeach other, and will again instantaneously change their position.

In a further, preferred embodiment, the pressure amplifier isdouble-acting, so that the impulse rod interacts with two high pressurepistons arranged on opposite sides of the operational chamber, andfurthermore there are provided two high pressure outlets.

Since the changeover valve is arranged concentrically around the impulserod inside the cylinder, in this embodiment it is possible to let theimpulse rod continue linearly through the changeover valve, and here bein contact with yet a high pressure piston. A further low pressureconnection is provided axially in parallel with the centre line in thelower pressure cylinder, whereby by changing the direction of supplywhen the changeover valve switches from one position to anotherposition, low pressure medium will be supplied at the opposite side ofthe main piston whereby this will imply high pressure to be formed atthe opposite end of the pressure amplifier.

In a further, preferred embodiment of the invention, high pressurepiston and impulse rod, respectively, are loosely connected to the lowpressure piston, e.g. by means of flanges provided at one end of thehigh pressure piston and the impulse rod, respectively, which flangeslargely fit a corresponding, partially closed recess provided in the endfaces of the low pressure piston, so that the flanges of the impulse rodare loosely held by means of locking rings.

In that connection, by loosely connected is meant that such a connectionis provided between the low pressure piston and the high pressure pistonand the impulse rod, respectively, that it is possible for the elementsto rotate, displace or in other ways perform turning/displacementindividually, without the coherent member necessarily being applied aload.

This is very important as the tolerances with which the high pressurecylinder and the main cylinder are joined thereby have lesssignificance, as well as possible wear over time will have lessinfluence on the operation of the pressure amplifier.

When it is possible to reduce requirements to the constituent elements,this implies a saving in the production step but also an increasedexpectancy of service life, as the wear is reduced by the movable partsdue to their ability of accommodating tolerances that may arise in thesystem due to heat action, wear, inaccuracies in the assembling stepetc. Besides, the assembly of the pressure amplifier also enablesrelatively uncomplicated disassembling of the pressure amplifier inconnection with service or replacement of individual parts. This is alsoassociated with low pressure piston and changeover valve operating inthe same boring with a uniform cross-section. The individual elementsare fitted by means of e.g. locking rings, so that the elements (lowpressure piston, impulse rod, changeover valve, spring etc.) by removingthe locking rings may be taken out of the cylinder, be inspected and tothe required extent be overhauled or replaced, after which the pressureamplifier may be assembled again without any problems.

The above mentioned advantages are even more expressed in a further,preferred embodiment of the invention, in which high and low pressurepistons, high and low pressure cylinders, check valves, high and lowpressure connections with associated springs and locking mechanisms arearranged co-axially and symmetrically around a common centre axis.

In an embodiment of the pressure amplifier according to the invention,the pressure amplifier housing consists of three assembled cylindricparts, in which internally a cylinder is provided, in which is arrangeda changeover valve and lower pressure piston and impulse rod, and in asecond cylinder, in immediate connection with the first cylinder, isarranged a high pressure piston with lesser diameter. In the highpressure piston end is installed a high pressure port via a check valve,and in the low pressure end there is arranged two gates as well, one forsupplying low pressure medium and one for medium returning to thereservoir.

Traditionally, when this type of typical hydraulically poweredcylinders, they being pressure amplifiers or other elements, are made,ducts are often to be provided perpendicularly to the centre line of theitem. This is normally done by radially drilling a hole from the outerside of the cylinder and into and through the internal cylinder cavityof the cylinder. Then a plug is fitted in the surface with theconsequent risk of leakages. This method for providing ductsperpendicularly to the centre line of a cylinder has several advantagesas long as the medium conducted in the duct does not have a particularlyhigh pressure. The plugs are normally usable up to a pressure about 500bar, after which the risk of failure, e.g. in the form of leaks, risessharply. In connection with development of the present pressureamplifier, where operation may take place with considerably higherpressure, this solution is thus not applicable. The connection betweentwo parallel medium ducts in the cylinder is therefore provided with aso-called T-cutter or another suitable tool for providing a radialmilled recess, forming connection between the two parallel axial ducts.

The radial recess thus provides a number of advantages, inter alia theradial drilling with subsequent plugging is avoided, which, besidessaving work procedures in connection with drilling and subsequentplugging, also increases safety for the operation of the pressureamplifier at high pressures, as the risk of a failure in a possible plugis not present. Besides, the effective flow area becomes substantiallylarger with a radial milled recess compared with the traditionaldrilling, whereby the invention is providing a considerably lesserpressure loss again compared with traditional constructions. Besidesincreasing the operative reliability and reducing the pressure loss, theincreased duct size also enables a higher rate of operation and therebya better utilisation of the entire pressure amplifier.

By the construction of the pressure amplifier according to the inventionas described above, the number of joints, plugs and other weak spots inthe pressure cylinder itself are avoided and minimised, why it is theother components in system that determine the dimensions for how highpressure to be operated with. The pressure amplifier is thus not limitedto the recommended maximum pressures in the system. Standard elementsused in high pressure hydraulic systems, may typically operate up to800-900 bar, but the pressure amplifier according to the invention hasshown that it may work reliably and safely at substantially higherpressures.

In a further, preferred embodiment, externally of the valve there isprovided an annular turning with a diameter less than the outer diameterof the valve and a length in longitudinal direction of the pressureamplifier, the length being substantially less than the length of thevalve, and that at least two holes are provided in the valve radiallyfrom the interior of the valve to the exterior of the valve, and thatone hole is provided coinciding with the annular turning, and that theother hole is provided outside the annular turning.

By this construction is achieved a hydrodynamic balancing, as it appearsthat by the pulsating pressure differences arising during operation withthe pressure amplifier, pressures can arise inside the valve being sogreat that it will expand and thereby become squeezed against thecylinder wall. Thereby it is not possible for the springs to move thevalve, why it also becomes impossible to achieve the instant release ofthe locking function. This is mainly caused by the fact that due to thehigh operating speed it is not possible to equalise the pressure via thefit between valve and cylinder. On the contrary, by providing an annularturning and at least two holes, there will thus be an immediateconnection between the pressure prevailing at any time at the operatingside to the outer side/interspace between the cylinder, so that it willimmediately be possible to equalise the pressure at the outer side andthe inner side, respectively, of the valve, whereby the valve will notbe jammed against the cylinder wall and may continually functionaccording to the purpose.

In a still preferred embodiment of the invention, for facilitating theassembling and disassembling of the connection between the impulse rod,which is passed through the changeover valve, and the low pressurepiston, a bayonet coupling has been provided. After inserting theimpulse rod in the low pressure piston, the rod is turned 90° andsecured with a locking bolt. The assembly is made with a sufficientradial clearance in order that the elements can operate unhinderedly.

The invention will now be explained in more detail with reference to theaccompanying drawing, wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates in principle the structure of a pressure amplifier,

FIG. 2 illustrates a double-acting pressure amplifier,

FIG. 3 illustrates a double-acting pressure amplifier,

FIG. 4 illustrates a detail of lock blocks,

FIG. 5 illustrates a detail of a connecting duct,

FIG. 6 illustrates an annular turning in the valve body,

FIG. 7 illustrates a locking mechanism, valve assembly and spring stop.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In FIG. 1 is illustrated the structure of a single-acting pressureamplifier according to the invention in principle. The pressureamplifier is built up around a operational chamber 29, which isdelimited by a cylinder 7. Within the operational chamber there isprovided a low pressure piston 26 which is connected to a changeovervalve 19 with an impulse rod 24. A high pressure piston 12 is providedin connection with the low pressure piston. Besides, a low pressure gate1 is arranged at one end of the pressure amplifier, the low pressuregate being controlled by the valve 19 is communicating via axial ducts 6with the operational chamber as well as a return line 16 from theoperational chamber conducts the pressure medium controlled by the valveback to a reservoir.

At the opposite end is arranged a high pressure outlet 15, which via acheck valve 14 is in one-way medium communication with the high pressurecylinder 13.

In FIG. 1, the low pressure piston 26 has been pressed forward to itsforemost position by means of the supply of low pressure medium throughthe low pressure gate 1 and the operational chamber 29. Hereby, the highpressure piston 12 is also pressed forward to the end in the highpressure cylinder 13. The low pressure inlet 1 will now bring lowpressure medium via the check valve 11 to the front side of the highpressure piston 12.

As long as the pressure demand in the high pressure outlet 15 is lessthan the low pressure minus the opening pressure in the check valve 11,14, the low pressure medium will flow directly to the place ofconsumption simultaneously with the low pressure medium via the checkvalve 11 pressing the high pressure piston 12 as well as the lowpressure medium 26 to the left.

This may be effected since the changeover valve 19 in this situation hasconnected the operational chamber 29 to the tank via the return duct 16,and the opposite end of the main piston is in permanent connection withtank via return duct 16.

At the return movement, the axially displacing disc 9 provided in thelow pressure piston loaded with the spring body 10 will hit theprojecting end 23 on the changeover valve 19 shortly before the finishof the return movement—(the situation is not shown in the Figure).

By continuous supply of low pressure medium via the check valve 11 tothe front side of the high pressure piston 12, this and therebysimultaneously the continued return movement of the low pressure pistonwill pre-stress the spring body 10 until a force is attained which iscapable of overcoming the locking force acting with the spring body 4 inthe locking mechanism, pressing the pin 18 past the chamfered sides 17on the locking items 3, the locking items being provided in a flat,round groove 45 in the cylinder.

Spring body 4 is arranged in radially oriented borings 43.

The changeover valve 19 will hereby move from the position shown in FIG.1 to a position where the pin 18 is secured at the opposite side of thechamfered ends on the locking items 3.

In this position, access is created from the low pressure gate 1 via thesupply duct 6 axially disposed in the cylinder body 7 to the opening 20in the changeover valve 19. Low pressure medium may hereby flow into theoperational chamber 29 and actuate the low pressure piston 26 to forwardmovement, whereby the high pressure 12 is also moved forward. The lowpressure medium in the high pressure cylinder 13 will then be subjectedto pressure, whereby the check valve 11 will close simultaneously withthe check valve 14 will open and allow high pressure medium to flow outthrough the high pressure gate 15.

As the low pressure piston is pressed forward due to the continuedsupply of low pressure medium through the low pressure gate 1 and theopening 20 in the changeover valve 19 into the operational chamber 29,the head 22 on the impulse rod 24 will be retarded in its free movementby contact with the recess inside the changeover valve 19. At thecontinued, forward movement of the low pressure piston, the nut 25screwed on the opposite end of the impulse rod 24 will provide apre-stressing of the spring 10.

As long as the impulse rod 24 may move freely in the stroke S, nopre-stressing of the spring 10 will occur. The stroke S is so adapted tothe full length of the cylinder that before the low pressure pistonreaches its end position, as shown in FIG. 1, a certain compression ofthe spring 10 will have occurred. By slow and intermediate operationfrequency, this pre-stressing of the spring disposed coaxially aroundthe impulse rod 24 and inside the low pressure piston 26 in the shownexample, will be sufficiently great that it will overcome the holding ofthe changeover valve, i.e. the grip of the locking mechanism around thepin 18, why this will be instantly released. At higher operationfrequencies, the inertia in the changeover valve 19 will provide thatthe spring force in the spring 10 does not have sufficient force toovercome the locking mechanism of the changeover valve. For this reason,mechanical contact has been arranged between the nut 25, the disc 9 andthe shoulder (the projecting end) 23 on the changeover valve 19,respectively, and in opposite direction between the head 22 on theimpulse rod 24, the changeover valve 19, the nut 25, the disc 9 andlocking ring 8.

This mechanical contact will bring the changeover valve to its middleposition, after which the spring 10, which is now tensioned the most,will provide for the rest of the movement.

In FIGS. 2 and 3, the principles in a double acting pressure amplifieris illustrated in two different forms, these pressure amplifiersoperating in principle according to the same principles as describedabove with reference to a single-acting pressure amplifier. Referencenumerals are the same in all Figures.

With reference to FIG. 2, an embodiment of the invention will beexplained. The pressure amplifier illustrated in FIG. 3 is largelyanalogous to that shown in FIG. 2. By supplying a liquid or gaseousdriving medium at a certain pressure to the gate 1 in the outer housing,this will, via the axial duct, be conducted to the two annular grooves32, 33 at the inner side of the cylinder 7. Depending on the changeovervalve, in this embodiment in the shape of the position of the internalcylinder bushing 19, the drive medium will flow on into one of theannular grooves 30, 31 on the outer side of the changeover valve andfrom here on through a number of holes in the bottom of the these intothe interior 29 of the cylinder and actuate the main piston 26 to bemoved in one or the other direction.

In the same way, the displaced medium on the opposite side of the pistoncan flow out through the holes in the cylinder bushing, further onthrough the grooves 30, 31 to the grooves 37, 38 and through the axialduct in the housing 7 to the return duct 16.

The internal bushing 19 forming the cylinder itself, is axiallydisplacing in the external housing 7. Hereby is achieved alternatingconnection for the driving medium on one or the other side of the mainpiston 26 and access for the flowing away of medium at the opposite sideof the piston.

In order to avoid disturbing influence due to different pressure on theend faces of the cylinder bushing, both of these are relieved to thereturn connection 16.

In order to achieve a rapid and constant change of direction of thisvalve construction, two circular, annular grooves 34 have been made, orone or more axial grooves, or two or more transverse wedge-shapedgrooves, at the outer side of the cylinder bushing 19. By means of alocking device, e.g. in the shape of one or more balls 35, wedges orpins with ball-shaped end wedges, or rollers loaded with a spring body,a rapid and secure valve shifting is achieved, when the locking force ofthis device is overcome. The two impulse springs 10, 36 are having sucha spring characteristic that they just have reached a suitablepre-stressing for disengaging the above mentioned locking device 35immediately before the end positions of the main piston. Thepre-stressing of the spring body in the locking and positioning device35 and the impulse springs 10, 36 will rapidly and precisely bring thechangeover valve to the reverse function.

For achieving a sure valve shifting at high operating speed inaccordance with the description of the invention as shown in FIG. 1, thelow pressure piston 26 and valve 19 via disc 9 and locking ring 8 arecoupled together.

This system provides a rapid and secure valve shift at high operatingfrequencies as well as by very slow, sneaking movements of the mainpiston. The latter is e.g. the case when using the actuator inconnection with pressure amplifiers for liquid or gases.

By means of the two outlet pistons 12, the axial movements aretransferred to the actual pump function.

The actuator shown on FIG. 3 functions in a corresponding way, but thedisplacing valve member is only provided inside the cylinder boringitself which is formed by the outer housing.

In FIG. 4, the locking items 3 used in FIG. 1 are shown in detail. Thechamfered points 17 are arranged so that they are just making contact inthe locked condition. Furthermore, the blocks 3 are spring loaded sothat a considerable force is required to press the blocks 3 away fromeach other via the edges 17 whereby the instant shift of operatingdirection is produced.

In FIG. 5 is illustrated how the invention also provides a new andsecure principle for providing connecting ducts perpendicularly to thecentre line of the item.

The connection ducts serve to connect the axial ducts, e.g. ducts forsupplying pressure medium to the operational chamber. Typically, theseconnecting ducts are made by boring radially to the centre line 44 fromoutside the item. The hole is then plugged, e.g. by screwing on aspecial plug. The invention, however, provides these connecting ducts bymaking a ring channel 39 around the valve boring 40. In the ring channel39 is then made, e.g. with a T-cutter, a radial recess 42, wherebyconnection to a duct 42 is formed in parallel with the valve boring 40.

In FIG. 6 is illustrated a further embodiment of the valve body 19 inwhich is provided a annular turning 48. Besides, two holes 46, 47 areprovided, the holes connecting the inner side of the valve body 19 withthe outer side of the valve body. One hole 46 is provided opposite tothe annular turning, whereas the other hole 47 is provided outside theannular turning. Thereby it becomes possible instantly to compensate forpulsating pressure on one and the other sides, respectively, of thevalve, so that the valve body 19 by very great or rapid changes inpressure due to the pulsating operative movement in the pressureamplifier is not jammed against the cylinder surrounding the valve 19.In this Figure, the cylinder is not depicted. By providing a annularturning 48 in the valve body 19 there is thus achieved a hydrodynamicbalancing in the valve body, whereby this, even under extreme operatingconditions, will operate reliably without risk of jamming in thecylinder.

FIG. 7 illustrates a further embodiment of the invention.

As distinct from the above mentioned embodiments, this example differsparticularly on these points:

1) The locking mechanism

2) The assembly of the valve

3) Fixed stops 51 for springs 10, 36

In this embodiment, the locking mechanism is provided as an independentbody which e.g. is screwed into the cylinder 7. With this is achievedthat it becomes relatively simple to replace the spring element 4 and/orthe ball/wedge locking device 35. This may be the case in connectionwith usual maintenance or in connection with a desired change in thepressure amplifier, e.g. by increasing the force (stronger spring) to beovercome before the valve shifts.

In this embodiment, assembly of the valve is performed by means of anoil tight bayonet socket. When the locking ring 21 is mounted, valve,impulse rod and low pressure piston are secured inside the cylinder 7.By using a bayonet socket, the impulse rod is pushed in, turned 90° andthen locked/secured by means of the locking bolt 50.

The fixed stops 51 prevent too great compression/squeezing of the spring10 and ensure correct rapid shift at high frequencies. Too greatcompression/squeezing may cause destruction of the spring, whereby theentire function of the apparatus may be destroyed.

The locking arrangement is, as described above, built up of springs 4that actuate balls, wedges or other locking elements 35 for engaging andholding of the changeover valve 19. In FIGS. 6 and 7, the grooves 30, 31in the changeover valve 19 are made as linear, transverse grooves 34.The corresponding locking elements 35 may advantageously be designed aswedges. With this embodiment is achieved a considerably better securingof the changeover valve 19, as the wedges 35 have a greater contactsurface on the grooves 34 than the balls (see FIG. 2) have on thecorresponding grooves 34.

1. Pressure amplifier including a low pressure inlet for supplying adrive medium at low pressure, a low pressure piston with a firstoperational area and at least one high pressure piston with a secondoperational area, the second operational area being of same size or lessthan the first operational area, and at least one high pressure outlet,wherein a low pressure area (1) communicates with an operational chamber(29), which is limited by the low pressure piston (26) and a surroundinglow pressure cylinder (7); where the at least one high pressure piston(12) is provided interacting with the low pressure piston (26), and theat least one high pressure piston (12) is co-axially arranged in a highpressure cylinder (13) relative to the low pressure piston; wherein achangeover valve (19) is coaxially arranged in the low pressure cylinder(7), and in connection with the changeover valve (19) there is arrangedat least one impulse spring (10,36) coaxially around an impulse rod(24); wherein the at least one impulse spring (10,36) is arranged to becompressed at the movement of the low pressure piston so that at leastone spring loaded locking mechanism (3, 35) is instantly released, thelocking mechanism being built up of one or more springs (4) that press alocking member (3, 35) against a corresponding lock abutment formed inthe changeover valve (19), so that the changeover valve shifts and opensfor the drive medium supply to the operational chamber whilesimultaneously the low pressure piston, via contact with the highpressure piston, is moving the high pressure piston towards the highpressure outlet (15), whereby the impulse rod (24) via the at least oneimpulse spring (10,36) and mechanical stops (8,9,22,23,25) in an endposition of the low pressure piston releases the locking mechanism (3,35) whereby the changeover valve shifts and the drive medium, via a lowpressure connection (6) via a check valve (11), presses the high and lowpressure pistons back.
 2. Pressure amplifier according to claim 1,characterised in that the locking mechanism is built up in at least oneboring provided radially in the low pressure cylinder (7), and that inthe boring a ball or a wedge (35) has been provided, the ball or wedgeinteracting with a spring (4) so that the ball or wedge (35) are presseddown into one of two recesses (34) with same dimensions as the part ofthe ball or wedge (35) provided in a cylindrical surface of thechangeover valve (19).
 3. Pressure amplifier according to claim 1,characterised in that the locking mechanism is built up in an annular,flat, round groove (45) provided at the inner side of the low pressurecylinder (7), so that at least two U-shaped locking members (3) arearranged in the groove, the locking members (3) being chamfered at theends (17), that a number of radially oriented borings (43) have beenprovided, corresponding to the number of locking members (3), and thatin each boring (43) there is arranged a spring (4) pressing the lockingmembers (3) towards the centre line (44) of the cylinder so that thechamfered ends (17) of the locking members co-operate hold a lockingelement (18) arranged in the valve in one of two positions on respectivechamfered sides (17) of the locking members (3).
 4. Pressure amplifieraccording to claim 3, characterised in that the pressure amplifier isdouble-acting so that the impulse rod (24) is interacting with two highpressure pistons (12) arranged at opposite sides of the operationalchamber (29), and that furthermore two high pressure outlets (15) areprovided.
 5. Pressure amplifier according to claim 1, characterised inthat the high pressure piston (12) and impulse rod (24), respectively,are loosely connected to the low pressure piston (26) by means offlanges that are provided at one end of the high pressure piston and theimpulse rod, respectively, the flanges (46) largely fitting incorresponding cavities provided in the end faces of the low pressurepiston so that the flanges are loosely held by means of locking rings(8).
 6. Pressure amplifier according to claim 1, characterised in thatthe high and low pressure pistons, the high and low pressure cylinders,the check valve and one or more additional check valves, the lowpressure connection and a high pressure connection with associatedsprings and locking mechanisms are arranged coaxially and symmetricallyaround a common centre line (44).
 7. Pressure amplifier according toclaim 6, at least one boring (40) and parallel axial connections(6,16,40,41) and annular channels (30,31,32,33,34,39) withinterconnection established by radial milling from inside the at leastone boring.
 8. Pressure amplifier according to claim 1, characterised inthat one or two of the pistons are used for driving a pump fittedthereon for pumping another medium than the drive medium, or for drivingother oscillating apparatuses.
 9. Pressure amplifier according to claim1, characterised in that externally of the changeover valve, an annularturning is provided with a diameter less than the outer diameter of thechangeover valve and a length in longitudinal direction of the pressureamplifier, the length being substantially less than the length of thechangeover valve, and that at least two holes are provided in thechangeover valve radially from the interior of the changeover valve tothe outside of the changeover valve, and that one hole is providedcoinciding with the annular turning, and that the other hole is providedoutside the annular turning.
 10. Pressure amplifier according to claim4, wherein the two high pressure outlets are brought together to acommon outlet.